Have you had a look at
www.TheAirlinePilots.com :: View topic - Questions on Autopilot ? That website if great for quickly skimming common questions and topics.
In my opinion, IAS and altitude hold are very clearly properties of the flight path - You're trying to maintain a certain 3dimensional profile.
Holding the pitch attitude says nothing about the 3D flight path, just something about how the aircraft is oriented.